9th Class (CBSE) Science: Natural Resources

Question: Name the three processes in which oxygen is used.

Answer: Combustion, respiration and in the formation of oxides of nitrogen.

Question: Name two natural resources available on the earth.

Answer: Water and air.

Question: Give one example of biotic component of the biosphere.

Answer: All animals, plants and micro organisms.

Question: Identify which of the following are not the part of biotic environment, soil, plants, fish, air, insects.

Answer: Soil, air.

Question: Name two oxides formed by burning of fossil fuels, which are responsible for acid rain.

Answer: The oxides of nitrogen and sulphur:

1. Sulphur dioxide and sulphur dioxide.
2. Nitrous oxide and nitrogen dioxide.

Question: Mention the two forms of precipitation in nature when the temperature of air is very low.

Answer: (i) Fog and smog, (ii) Hail, (iii) Mist, (any two)

Question: Name the factor responsible for change in rainfall patterns in India.

Answer: Rainfall patterns are decided by the prevailing wind patterns. In large part of India, rains are mostly brought by South-West or North-East monsoons.

Question: Combustion of fossil fuels results in the increase of suspended particles in the air. What are these particles?

Answer: The suspended particles in the air could be unburnt carbon particles or hydrocarbons which lead to smog.

Question: How the frozen water between cracked rocks causes the cracks to widen?

Answer: The water inside the cracked rocks expand on freezing. When it expands, its volume increases and it causes the cracks to widen.

Question:0 Name two gases which cause greenhouse effect.

Answer: (i) Carbon dioxide, (ii) Methane, (iii) Oxides of nitrogen, (any two)

Question: Name two biologically important compounds that contain both oxygen and nitrogen.

Answer: Proteins and nucleic acids (DNA and RNA).

Question: Name two essential biological molecules in which oxygen is present.

Answer: (a) Proteins, (b) Carbohydrates, (c)‘ Fats aid lipids, (d) Nucleic acids, (any two)

Question: Name two biologically important compounds that contain both oxygen and nitrogen.

Answer: Proteins and nucleic acids (DNA and RNA).

Question: What is the greenhouse effect?

Answer: Some gases prevent the escape of heat from the Earth. An increase in the percentage of such gases in the atmosphere would cause the average temperatures to increase worldwide and this is called the greenhouse effect.

Question: The atmosphere acts as a blanket, how?

Answer: Air is a bad conductor of heat which keeps average temperature of the Earth steady during day and at night. The ozone shield of the atmosphere absorbs most of the harmful radiations coming from Sun.

Question: Name four human activities which cause air pollution.

Answer:

1. Mining activities: Dust released due to mining activities.
2. Thermal power plants: Fossil fuel burnt in these places causes air pollution.
3. Firework on festivals: It results in the release of toxic chemicals into air along with hot and toxic gases.
4. Burning of fossil fuel: In industries, automobiles, domestic purposes etc.

Question: Name the stages of the life cycle of aquatic animals which are affected by change in temperature.

Answer: The eggs and larvae of various aquatic animals are susceptible to temperature changes. As the aquatic organisms are used to a certain range of temperature in the water body where they live, and sudden marked change in this temperature would be dangerous for them or affect their breeding.

Question: How do sun and wind influence the formation of soil?

Answer: The Sun: The Sun heats up rocks during the day so they expand and at night they cool down and contract. This results in the formation of cracks and rocks ultimately break up into smaller pieces.

Wind: Strong winds help in the formation of rock particles by their erosion actions. This helps in formation of soil,

Question: Define weathering. Write the different means which cause weathering.

Answer: The process of breaking down of rocks into small, fine mineral particles is called weathering.

• The weathering may occur due to physical, chemical or biological means.

Question: Write the composition of soil. On what basis is the type of soil decided?

Answer: Soil is a mixture. It is composed of small particles of rocks of different sizes, humus (bits of decaying living organism) and various micro-organisms.

• The type of soil is decided by the average size of particles found in it.